Oxygenated derivatives of arachidonic acid (eicosanoids) produced by inflammatory cells have been demonstrated to act as potent mediators of inflammation and allergy. Eicosanoid generation is thought to be initiated by the mobilization of arachidonic acid from membrane phospholipids. However, arachidonic acid movement into and from cellular arachidonate pools has been shown to be a complex process involving many different enzymes and phospholipids. A central premise of the current proposal is that the diversity of arachidonate-containing pools and the enzymes which maintain that diversity are key features which enable inflammatory cells to regulate eicosanoid biosynthesis. Two principal hypotheses that this proposal addresses are: 1) that there are segregated pools of arachidonate-containing phospholipids within the mast cell that serve as independent sources of arachidonic acid for individual products; and 2) that arachidonic acid remodeling between phospholipid pools play an important role in moving arachidonic acid into the salient AA pools needed for eicosanoid biosynthesis. The current aims represent a logical extension of the PI's work supported as a R-29 (first award, AI-24985) from March 1988 to the present time. Experiments in aim 1 of this proposal will examine the question of whether there are independent cellular AA sources which release arachidonic acid destined to form leukotrienes, prostaglandins or remain as free fatty acids. The second aim will pursue a proposed model for arachidonic acid movement between the major phospholipids by better defining the fatty acids, phospholipids and enzymes which participate in the model. Aim 2 will also be directed at determining whether cell priming and activation change parameters of arachidonic acid remodeling between phospholipids. The major focus of this grant will be mast cells/however, other inflammatory cells will be used in selected experiments to determine whether findings obtained in mast cells are generally applicable. High resolution chromatography techniques combined with GC/MS analysis will provide sensitive and selective assays for arachidonic acid, lyso phospholipids and arachidonate-containing glycerolipids. Furthermore, mass measurements (GC/MS) together with isotopes measurements are utilized throughout this proposal as a means to quantitate lipid turnover and examine precursor-products relationships.